Navigation systems which make it possible to display to the driver of a vehicle navigation icons for a calculated route, are known from the state of the art. In these systems, the navigation icons above all show the progression of the calculated route at the relevant junctions. Conventionally, navigation systems access CD-ROMs integrated in the vehicle, for calculating the route and for the navigation icons to be shown, said CD-ROMs providing a large amount of storage space.
However, more modern navigation systems provide for route guidance to be already provided, from an external service provider, by way of a radio link. This not only makes possible route guidance independent of a given vehicle, but also more flexible updating and enlargement of the services offered. If the service provider offers services via the Internet, the driver in the vehicle can for example use an Internet-capable or WAP-capable mobile telephone whose display shows the navigation icons for route guidance, with communication with the service provider taking place by way of said mobile telephone.
However, as an alternative, communication between the service provider and the driver of the vehicle can also take place via SMS (Short Message Service).
To use such a system it is necessary for the driver of the vehicle to enter the starting point and the desired point of destination in his/her terminal, and to transmit these to the service provider. However, the starting point can for example also be determined automatically from the current position of the vehicle. As an alternative, the point of destination could also be specified via a telephone call to the service provider.
After this, the service provider calculates the optimal route for the vehicle and transmits respective information concerning route guidance back to the terminal. When calculating the route, factors such as current traffic reports can also be taken into account. The terminal evaluates the information concerning route guidance during the trip and at every relevant junction shows a diagram of the junction on a small display of the terminal. In addition, the respective instruction can also be output via an acoustic output unit.
Such off-board systems are associated with a problem in that for extended routes large quantities of data need to be transmitted if individual files are transmitted for every intersection along the route. As an alternative, the terminal would have to comprise a storage device of sufficient capacity to store all navigation icons that may be used.
Printed publication U.S. Pat. No. 5,654,892 describes a navigation system which displays representations of one or two upcoming junctions. To this effect, a stored symbol showing the currently required type of junction or the currently required combination of junctions, appears on the display. Storing displays of all options of turning off, and in addition, all possible combinations of two options of branching off in sequence, requires a large amount of storage space which can be provided only if a respective storage medium is available in the vehicle, with the terminal being able to access said storage medium. Otherwise, it is only possible to offer a relatively limited selection of displays, thus hindering exact and clear route support. The printed publication also mentions that the respective display can be calculated, but no further information for implementing such a calculation has been provided.
The printed publication U.S. Pat. No. 4,937,570 describes a navigation system comprising a multitude of intersecting display segments in different colours which display various routes. To display an actual route, the respective segments are activated so that they are illuminated in the colours provided. This system requires less storage space because for each route only a reference to the segments to be activated has to be stored. However, said system lacks flexibility because it is restricted to those routes which can be shown by the display segments provided.